Ratchet jack



Nov. 29, 1932. F. H. QSCHWERIN RATCHET JACK Filed March- 24, 1952 7 lfiaTZR BY I Q ATTORNE Patented Nov. 29, 1932 UNITED STATES PATENT, OFFICE FRANK H. SCHWERIN, or IBELLEVUE, PENNSYLVANIA, ASSIGNOR 'rornn DUFF-NORTON MANUFACTURING COMPANY, OF PITTSBURGH, PENNSYLVANIA, A CORPORATION 01" PENNSYLVANIA RATCHE'I JACK Application, filed March 24, 1932. Serial No. 600,838.

This invention relates to jacks, and particularly to ratchet acks of the type in which a rack is slidably mounted in a supporting frame and raised by means ofa lifting pawl,

which is operated by suitable lever means. In jacks of this type, the rack is held in raised position by means of a holding pawl.

It has long been common practice to pivotally mount the holding pawl in the frame in such position that the action of gravity will urge the holding pawl into engagement with the teeth of the rack. Such construction has been improved by using spring means to supplement the action of gravity and insure more positive operation of the holding pawl, thus preventing accidental lowering of the jack, when under load, caused by the holding pawl not fully engaging the teeth of the rack.

WVith ratchet jacks of the trip type, the lifting and holding pawls may both be released simultaneously to effect a quick lowering of the jack, or the jack may be lowered with a step-by-step movement by alternately releasing the lifting and. holding pawls manually in a well known manner, commonly referred to as fingering-down the jack.

The frame of the jack is always provided with openings, through which access may be had' to thepawls for fingering down, and other openings are provided to lighten the weight of the frame. Since lifting jacks are ordinarily subjected to rough handling and is often dropped into tool boxes with rail plates and tools, any delicate parts, such as springs,

are very likely to be damaged orbroken unless enclosed within the frame and protected from striking against tools or other obstructions.

An object of this invention is to provide a jack construction having a spring for urging the holding pawl into engagement with the rack, the spring being designed and located so that the major portion thereof is completely protected against damage from rails, tools or other objects which may strike the jack and project through one of the openings in the frame. i

VVhen a ratchetjack'is equipped with a gravity-operated holding pawl, the effect of gravity in urging the holding pawl into engagement with the rack'becomes increasingly less as the pawl moves toward a substantially vertical position in which it ordinarily engages the teeth of the rack. With the holding pawl in a truly vertical position, the force of gravity'would no longer have any effect to. urge the holding pawl toward the rack.

Where springs have been used to supplement the force of gravity in urging the hold-. ing pawl into engagement with theteeth of the rack, the springs have been mounted so that the spring force against the pawl is lightest when the holding pawl is in substantially vertical position, and increasingly heavier as the pawl is moved away from the rack. This design is just the opposite to what it should be for efficient operation of the jack, and the increasing load as the pawl moves away from the rack makes the fingering-down of the jack very difficult and sometimes uncertain.

An object of this invention is to provide a spring-loaded holding pawl, in which the force of the spring increases as the pawl moves toward the jack, thus placing the maximum spring pressure against the pawl when it is most needed to insure complete engagement of the pawl with the teeth of the rack.

A more particular object of the invention is to provide a hanging, gravity-operated holding pawl with a. spring to supplement the action of gravity in such a way that the spring force increases as the pawl moves in a direction so that the urge of gravitydecreases, and vice-versa.

Other objects and advantages of the invention will appear and will be pointed out as the description proceeds.

In the accompanying drawing, forming a part hereof:

Fig. 1 represents a diagrammatic side ele vation of a lifting jack, made in accordance with this invention;

Fig. 2 is a fragmentary side. elevation, showing the other side of the ack illustrated in Fig. l; and v I Fig; 3 is asectional view on the line 3-3 of Fig. 1. Y

A rack 11 is slidably mounted in a supporting casing or frame 12. The rack 11 is provided with teeth 13.

A lifting pawl 14 is operated by suitable lever means, such as the operating lever 16, which is pivotally mounted at 18 on the frame 12. A holding pawl 19 is pivotally mounted at 20.

The jack is operated in the conventional manner by the operating lever 16, which moves the lifting pawl 1% by repeated steps, the holding pawl 19 acting to prevent lowering of the rack 11 during the alternate downward movements of the lifting pawl 14c.

The pivotal mounting 20 is located so that the holding pawl 19 will be slightly inclined when in position to engage the teeth 13. Owing to this inclination, the action of gravity on the holding pawl 19 will always urge the holding pawl into engagement with the teeth of the rack. The construction thus far described is conventional.

In order to insure a more positive action of the holding pawl 19 when engaging the teeth of the rack 11, a spring 22 is provided.

This spring is mounted on a stud 24, which is secured to the frame 12. The lower end of the spring 22 contacts with an inside wall of 7 the jack frame and the upper portion of the spring 22 contacts with a stud 26, which serves as a spring-engaging portion of the holding pawl. From the above description of the spring mounting, it will be apparent that the spring 22 acts with a cantilever action.

The stud 26 is preferably provided with an annular recess 28, in which the spring 22 operates. This annular recess prevents lateral displacement of the upper portion of the spring 22. As the holding pawl 19 moves about its pivotal mountin 20, the spring 22 slides on the stud 26 with a cam-like action.

The upper portion of the spring 22 is shaped so that the force of the spring against the stud 26 will be more nearly tangent to the movement of the holding pawl 19 when the holding pawl is in position to engage the teeth of the rack. As the holding pawl 19 moves away from the rack, the direction in which the spring force is applied becomes less tangent to the movement of the holding pawl 19. Due to this design of the spring, the spring force tending to move the holding pawl into engagement with the rack becomes increasingly greater as the holding pawl moves toward the rack. and increasingly less as the holding pawl moves away from the rack. Thus, the action of the spring 22 supplements the action of gravity in a very eiiicient manner, since the force with which gravity urges the holding pawl into engagement with the rack decreases as the holding pawl approaches the substantially vertical position in which. it engages the teeth of the rac The lifting pawl 14 is provided with an extension 28, which projects through an opening 80 in the side of the jack frame 12. The holding pawl 19 is provided with an extension member 32, which also projects through the opening 30 and is located close enough to the extension member 28 so that these extension members 28 and .32 may be conveniently used to alternately release the lifting and holding pawls when lowering the jack with a step-bystep operation, commonly referred to as fingering-down the jack. The extension members 28 and 32 are located on the side of the jack remote from the spring 22, so that the spring 22 will not in any way obstruct an operator when manipulating the pawls by means of the extension members.

The spring 22 is mounted within the frame 12 in such a manner that only a minor por tion of the spring 22 extends beyond the open part of the jack frame. The major portion of the spring 22 is, therefore, completely protected by the jack frame against damage or breakage which might be caused by a rail or tool striking against the side of the jack.

The invention is illustrated in its preferred embodiment, but various changes and modifications may be made, particularly in the shape of the spring 22, without departing from the spirit of the invention as set forth in the appended claims.

I claim:

1. Aj ackincluding, in combination, a frame a rack slidably mounted in the frame: a lifting pawl; lever means for operating the lifting pawl; a holding pawl pivotally mounted on the frame; extension means connected with the holding pawl and operable to shift the holding pawl about its pivotal mounting;

other extension means connected with the l fting pawl and located adjacent the holding pawl extension means for convenient operation of both extension means when operating the pawls to lower the jack with a stepbvstep movement; a spring-engaging portion on the holding pawl and remote from the extension means; and a spring mounted on the frame and connecting with said engaging portion to urge the holding pawl into engagement with the rack.

2. A jack including, in combination, a frame; a rack slidably mounted in the frame; a lifting pawl; lever means for operating the lifting pawl; a holding pawl pivotally mounted on the frame; and a spring tensioned between the jack frame and the holding pawl in such position that the spring urges the holding pawl into engagement with the rack with a force which decreases as the holding pawl is moved away from the rack.

3. A jack including, in combination. a frame; a rack slidably mounted in the frame; a lifting pawl; lever means for operating the lifting pawl; a holding pawl pivotally mounted on the frame; a cantilever spring mounted on the frame and extending adjacent the holding pawl; and a spring-engaging portion, on the holding pawl, in position to engage this spring with a cam action as the pawl moves toward and from the rack.

4. A ack including, in combination, a frame; a rack slidably mounted in the frame; a lifting pawl; lever means for operating the lifting pawl; a holding pawl pivotally mounted on the frame in position so that it is urged against the rack by the action of gravity when the jack is in normal working position; and a spring contacting with the holding pawl to urge said holding pawl against the rack; and means holding the spring in position so that the urge of the spring is greatest with the holding pawl in the position where the urge of gravity is least, and the urge of the spring least with the holding pawl in position where the urge of gravity'is greatest.

5. In a lifting jack, asupporting casing; a rack slidably mounted in the casing; a lifting pawl; lever means for operating the lifting pawl; a holding pawl pivotally mounted on the supporting casing to assume a substantially vertically hanging position when engaging the teeth of the rack; a cantilever spring mounted on the casing and contacting with the holding pawl to urge it into engagement with the rack; and means for securing the spring in position so that the force of the spring against the holding pawl is greatest when the holding pawl is in substantially vertical position, and decreases as the holding pawl is moved toward a horizontal position.

6. In a ratchet lifting jack, a supporting casing having openings therein; a lifting pawl; lever means for operating the lifting pawl; a holding pawl pivotally mounted within the casing, certain of the openings in the casing being in position to provide access to said pawls; spring means within the casing tensioned between the casing and the holding pawl so as to urge the holding pawl into engagement with the rack; and means for retaining the spring means in position so that the major portion of the spring means is located behind a closed part of the supporting casing and thereby protected against damage by an implement striking the ack.

7 In a ratchet lifting trip jack, a supporting casing having openings therein; a lifting pawl; lever means for operating the lifting pawl; a holding pawl pivotally mounted within the casing; an extension member connected with each of the respective pawls and extending through one of the openings in the casing for convenient operation in fingeringdown the jack; a cantilever spring mounted within the casing and contacting with the holding pawl at a point remote from the extension members; and means for securing the cantilever spring to the casing in position so that the major portion of the spring is located behind a closed part of the supporting casing and thereby protected against damage by an implement striking the jack.

FRANK H. SGHWERIN. 

